SEM is a type of Internet marketing associated with the researching, submitting and positioning of a website within search engines to achieve maximum visibility and increase your share of paid and/or organic traffic referrals from search engines.

SEO and SEM are not competing services. SEO is considered a subset of SEM services. Today, if you want to conduct business on the Internet you need to be visible in both organic and advertised links, which means you need both SEO and SEM.